The importance of milk in the diet
One of the first foods in the human diet is milk, and knowledge of it and its properties dates back to the first years of our era [1]. Scientific studies provide ample evidence that milk and its products are a superb source of proteins, fats, sugars, and micro- and macronutrients.
This, in turn, makes milk one of the most valuable components of the daily human diet. It is also the best and, at the same time, the cheapest available source of calcium [2]. It is therefore not surprising that a continuous increase in the consumption of milk and milk products has been recorded in Poland since 2006. In 2019, the average Pole consumed 225 litres of milk and 5.4 kilograms of butter [3].
What can we find in milk?
As an excellent source of many nutrients, milk contains, among other things, lactose, which is essential for the normal development of the nervous system. Furthermore, lactose is converted to lactic acid in our body. This, in turn, stimulates the development of intestinal flora and increases the assimilation of micro- and macronutrients.
Milk is also one of the best sources of calcium. In addition, it is not lacking in magnesium and zinc, which not only support immune processes but are essential for the body to function properly. It also contains bromine, manganese, iodine, and fluorine [2, 6, 7]. It is worth noting that milk is also rich in fats. These are mostly simple fats, such as glycerol and fatty acid esters. In addition to these, phospholipids necessary for the construction of brain tissue and carotenoids that facilitate the conversion of vitamin A to its active form are also present [6].
Proteins cannot be overlooked in the composition of milk. There are about forty of them, and thirty of those are capable of causing an allergy. Four of these are the most common to cause allergies [4]. These include casein, which comprises about 75% of all proteins [4]. It is what gives milk its white colour. The remaining three proteins are the so-called whey proteins. These include α-lactalbumin, β-lactoglobulin and bovine serum albumin. They are used, for example, in protein supplements for athletes. [1, 4, 5, 6].
Milk allergy or lactose intolerance?
Milk protein allergy is often confused with lactose intolerance, one of the milk proteins. The two conditions are not identical. However, they can be difficult to distinguish due to similar clinical gastrointestinal symptoms.
- Approximately 37% of Poles are deficient in lactase, the enzyme that breaks down lactose. This mechanism is responsible for lactose intolerance [8]. It is present primarily in mammalian milk, but also in many foods. It is mainly responsible for improving their palatability [9].
- The symptoms of lactose intolerance mainly affect the gastrointestinal tract. They may include abdominal pain, diarrhoea and vomiting, flatulence and a feeling of overflow. They usually appear shortly after consumption of lactose-containing products [9].
- An allergy, on the other hand, is a systemic disease that develops as a result of hypersensitivity of the immune system to a particular stimulus. Milk contains, approximately, 30 proteins that can cause it.
Cow’s milk allergy is quite common and affects around 1.9 – 4.9% of Poles. The group most frequently affected by milk allergy are children under 3 years of age. This percentage decreases steadily with age, as many patients develop tolerance to this antigen over time [12].
Milk allergy symptoms
The clinical manifestations of cow’s milk allergy mainly involve the gastrointestinal tract, the respiratory system, and the skin.
- On the gastrointestinal side, the following are observed: diarrhoea, vomiting, abdominal pain.
- Skin symptoms include: itching, hives, erythema.
- In the case of the respiratory system, allergies manifest themselves as swelling of the nasal mucous membranes, a watery nose, sneezing or a dry cough.
Symptoms usually appear immediately after the ingestion of the allergen, but some of them, e.g., urticaria or abdominal pain, may only occur after a few days [10].
Diagnosis of a milk allergy
Once you observe symptoms that may indicate a milk allergy, you should visit an allergologist. The initial diagnosis of cow’s milk allergy is not very different from the diagnosis of other food allergies. The first step is a medical history, which should confirm a link between milk consumption and the presence of symptoms.
Subsequently, the physician may order a point-of-care skin test, the determination of specific E antibodies in serum or a food provocation test [11].
Once a cow’s milk allergy has been diagnosed, molecular tests can be taken a step further. These will determine which molecules, i.e. specific cow’s milk proteins, are the cause of the condition. The individual substances differ in their patient-relevant properties. Molecular diagnostics makes it possible to determine, among other things, what is the risk of anaphylactic shock, whether the patient can consume heat-treated milk, what is the risk of cross-reactivity with other allergens or, in the case of allergy in children, what is the chance that the condition will persist into adulthood [1,12].
It is worth emphasizing at this point that a finding of allergy to milk does not necessarily mean that it has to be eliminated from the diet in all its forms. Based on the results of the molecular tests, the doctor will be able to make individual recommendations for the patient. You will be able to read more about allergies to individual cow’s milk proteins in future articles.
S. Gałązka, W. Borkowska, R. Śliwa, W. Ziemichód
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translation: Julia Majsiak
